Fibrous insulation products are available in various densities for use in a variety of different environments. One such product is a lightweight glass fiber blanket used to insulate structure which requires a high degree of insulation, such as aircraft hulls. In such an environment it is important that the weight be minimal so as not to add unnecessarily to the weight of the aircraft, and that the blanket be capable of providing an effective barrier to the high sound levels and cold temperatures encountered during flight.
Typical products now in use are comprised of fine glass fibers bonded together in blanket form and having a density of about 0.3 pound per cubic foot (pcf) to 1.5 pcf. Depending on the dimensions of the space required to be insulated, either a single blanket or several stacked blankets are wrapped and secured within a film, as by sewing or heat sealing, and the wrapping insulation is then attached to the aircraft fuselage by pins connected to the skin of the aircraft. In addition to holding the wrapped insulation in place, the pins prevent the insulation blankets from shifting with respect to each other. Due to the fragile nature of the insulation, a great many pins are required to satisfactorily hold the blankets in place. For example, it is not uncommon for as many as 10,000 pins to be used to install insulation in a large aircraft. This is not only a time consuming operation, but the cost of the pins themselves is expensive. Also, because the operation compresses the insulation blanket in the area surrounding the pins, some of the insulation performance value may be sacrificed.
While such products perform their insulating function satisfactorily, certain of their other characteristics could advantageously be improved. For example, although the low density, lightweight construction of the blankets makes them quite suitable as insulators, it also results in minimal physical properties, making the products susceptible to damage. In particular, the relatively low tensile strength of the product offers little resistance to stresses encountered during fabrication and installation. This is especially so in environments where the product is placed under tension by being wrapped about a structure. Handling of the individual layers and fabrication of the multi-layered product subject the material to additional stresses which tend to damage the weak fiber glass material.
In addition, the effectiveness of insulation wrapped in a film is likely to be reduced in service by condensation of water vapor trapped within the insulation. Because the commercial product usually requires an outer film to allow the insulating blanket to be handled and installed as desired, there would appear to be no easy solution to this problem.
It can be seen from the foregoing that it would be beneficial to improve the tensile strength of a blanket of fibrous insulating material without impairing its insulating ability and without adding significantly to its cost or weight. It would also be beneficial to be able to eliminate the condensation problem without adversely affecting the product.